Postsynthetic Metal Exchange in a Metal-Organic Framework Assembled from Co(III) Diphosphine Pincer Complexes.

A Zr metal-organic framework (MOF) 1-CoCl3 has been synthesized by solvothermal reaction of ZrCl4 with a carboxylic acid-functionalized CoIII -PN NN P pincer complex H4 (L-CoCl3 ) ([L-CoCl3 ]4- = [(2,6-(NHPAr2 )2 C6 H3 )CoCl3 ]4- , Ar = p-C6 H4 CO2 - ). The structure of 1-CoCl3 has been determined by X-ray powder diffraction and exhibits a csq topology that differs from previously reported ftw-net Zr MOFs assembled from related PdII - and PtII -PN NN P pincer complexes. The Co-PN NN P pincer species readily demetallate upon reduction of CoIII to CoII , allowing for transmetalation with late second and third row transition metals in both the homogeneous complex and 1-CoCl3 . Reaction of 1-CoCl3 with [Rh(nbd)Cl]2 (nbd = 2,5-nobornadiene) results in complete Rh/Co metal exchange at the supported diphosphine pincer complexes to generate 1-RhCl, which has been inaccessible by direct solvothermal synthesis. Treating 1-CoCl3 with PtCl2 (SMe2 )2 in the presence of the mild reductant NEt3 resulted in nearly complete Co substitution by Pt. In addition, a mixed metal pincer MOF, 1-PtRh, was generated by sequential substitution of Co with Pt followed by Rh.